more information on this research and on no-till cover
crop mulch systems for organic vegetable production,
contact: Dr. Ron Morse, Professor of Horticulture,
Virginia Tech., Blacksburg, VA 24061; tel. 540-231-6724;
and how organic no-till got started
Weed control is often cited as the single greatest
challenge in organic crop production. In relying on
tillage and cultivation rather than chemical herbicides
to manage weeds, organic growers risk greater soil degradation,
organic matter loss and erosion. Cover crops suppress
weeds, add organic matter and nitrogen, mobilize nutrients,
hold and improve the soil, and harbor beneficial insects.
However, when the cover crop is turned under prior to
planting the primary crop, the tillage required to prepare
a seedbed burns up organic matter, degrades tilth and
stimulates weeds to emerge—which means yet more
cultivation and associated costs.
Since the mid 1980s, researchers at the New Alchemy
Institute, The Rodale Institute Experimental Farm, and
several land-grant universities have experimented with
managing winter annual cover crops such as rye, hairy
vetch, and crimson clover without tillage prior to planting
a vegetable crop. These cover crops can be killed mechanically
by mowing or rolling after they begin to flower and
shed pollen (usually in mid to late May), and the resulting
mulch can suppress weeds for six weeks or more. During
this time, tomatoes, broccoli or other vegetables can
be transplanted and established so that later-emerging
weeds have little impact on yield.
look forward to learning more about the effects of no-till
on the soil, crop yields, weed and pest levels, and
net economic returns to the farmer. Stayed tuned to
for updates on project findings over the next few years.
pros and cons of no-till cover crop management
The potential advantages of this system include greater
cover crop biomass production (since it is allowed to
grow until a week or so before vegetable planting),
and much less loss of organic matter through tillage.
Together, these can greatly enhance annual organic inputs
and thereby support higher levels of 'active organic
matter,' which correlates closely with soil quality.
In addition, the cover crop mulch conserves soil moisture,
curbs weed seed germination, and provides habitat for
ground-dwelling predators of insect pests.
On the other hand, continuous no-till can eventually
lead to perennial weed problems or cause some soils
to become somewhat compacted. Thus organic growers may
need to practice 'rotational tillage,' working the soil
before planting cover crops in some years. Research
results at The Rodale Institute Experimental Farm suggest
that this may be the case. How often tillage is needed
and whether soil quality can still improve under rotational
tillage are two of the questions Morse’s research
One other possible drawback is that the cover crop
mulch will keep soil temperatures lower so that the
system may not work where early harvests are desired,
especially for warm season crops. However, later plantings
of the same crops may benefit from the soil-cooling
and moisture-conserving effects of mulch, especially
in hot climates or in drought years.
||“The one thing I
want to accomplish before I retire is to establish workable systems
for organic no-till vegetable production using cover crops,”
Dr. Ron Morse told me in one of our first meetings. A professor of
horticulture at Virginia Tech, in Blacksburg, Va., Morse has been
working for upwards of two decades on soil-conserving systems for
vegetable production in hilly Appalachia. Using high-biomass cover
crop mixtures like winter rye and hairy vetch killed to form an in
situ mulch, he has helped growers save tons of soil and reduce weed
control costs. More recently, he has worked on herbicide-free systems
for organic growers.
Morse was born and raised on a family farm in Utah. He worked with
his father and three brothers in their 10-cow dairy, where “we
did everything together, which taught us a strong ethic of cooperation
and responsibility.” He went to college at Utah State, then
earned a Ph.D. in Horticulture at Michigan State. His professional
commitment to making farming more sustainable for both land and
grower led naturally to no-till cover crop systems.
Morse began this line of research in the winter of 1978-79, when
he received a letter from an extension agent in mountainous Carroll
County, Va., with a photo of U.S. Route 58 blocked by a mass of
soil washed away from an adjacent cabbage field. The caption read
simply, “Help!” Morse knew the first step was to stop
plowing. So he put a graduate student to work at Virginia Tech’s
experimental farm, growing rye cover crops for no-till vegetable
planting. Initially, they planted by hand, digging holes to plant
cabbage through herbicide-killed rye. It worked!
The next hurdle was to mechanize the transplanting. At first, researchers
modified a Holland transplanter by adding a front coulter to slice
through cover crop residues, which worked well in moist, mellow
soils. Farmers got interested fast—but then a drought struck,
and the Holland planter repeatedly broke when pulled through dry,
untilled soils. So Morse and a team of others built the first Sub-Surface
Tiller-Transplanter (SST-T) in 1990. The front component is a durable
sub-surface tiller that prepares a narrow strip of soil, loosening
as deep as 8 inches. The second is a no-till transplanter that sets
transplants into the prepared strip. It has a double-disk opener
ahead of the planting shoe, and the press wheels are modified so
that they close the untilled soil around the plant. By 1996, improved
versions of the SST-T could lay drip tape, apply organic or conventional
fertilizer (in-row or side-band), and water in the transplant. Different
attachments can be used for a variety of vegetable starts, seed
potatoes or large seeds like beans.
If you build it, they will come
When word of early successes got out, Morse received an avalanche
of calls from farmers and extension agents wanting to see demonstrations
and try the SST-T themselves. Many calls came from organic farmers
and sustainable agriculture organizations interested in better weed
control with less soil-damaging tillage. So the herbicides had to
go—and winter annual cover crops can be killed mechanically.
Morse uses a flail mower or a roller-crimper to convert a live,
standing cover crop into a mulch through which the SST-T can easily
operate. (A bush-hog or a sicklebar mower leaves the cover crop
stems helter-skelter, which can jam the planter.) Broccoli, potatoes,
tomatoes and other vegetables have been successfully planted into
flail-mowed cover crops at Virginia Tech’s Kentland Agricultural
Research Farm (hardiness zone 6b) and on several organic farms in
the region. “The key to success is to grow really good cover
crops,” Morse emphasizes, “at least three tons dry matter
per acre. I like the rye and vetch [mixture] to be five or six feet
high, and nice and thick. Otherwise, you don’t get weed control.”
Morse and his colleagues are also experimenting with other cover
crops and planting seasons. Frost-tender annuals like German or
foxtail millet, pearl millet, sorghum-sudan hybrid (sudex), cowpeas,
forage soybean, sunn hemp, or lablab bean can be planted in early
summer and mowed in August for no-till fall brassicas, or planted
later in summer and grown until killed by fall frost. Sudex produces
tremendous biomass, and suppresses weeds through competition and
allelopathy (the release of substances that inhibit weed growth).
Mowing sudex when it is chest high stimulates roots to penetrate
deeper, which opens the subsoil and may enhance allelopathy. Morse
mixes stiff-stemmed grasses or sunn hemp with more succulent legumes
to maximize biomass and ground cover, and to balance the carbon
to nitrogen ratio. Fall broccoli planted no-till into a flail-mowed
cowpea and sunn hemp mixture gave yields similar to conventional-till
Oats, lana vetch and berseem clover tolerate frosts to 20 degrees
but do not over-winter, so they can be planted in late summer to
create a winter-killed mulch for no-till planting of brassicas or
other early spring crops the next year. When frost kills the cover
crop, mowing is not needed.
Cover crop systems are limited only by your imagination
The possibilities are limited only by the imagination, of which
Morse has plenty. He grows self-seeding winter cover crops such
as little barley (considered a weed by some) and subterranean clover,
which die down in early summer and come back from seed in the fall.
In mid July 2003, he planted ‘Arcadia’ broccoli no-till
into a little barley and sub clover residue. Recently, he began
experimenting with garlic, which is normally planted in October
and immediately mulched with hay or straw. This fall, he planted
garlic no-till into frost-killed sudex, sunn hemp and lablab beans.
For no-till vegetables, Morse usually forms a raised bed just before
planting the cover crop. At Kentland Farm, he plants “companion
grass,” a mixture of dwarf perennial ryegrass and creeping
red fescue, in the alleys between beds and up the bed shoulders.
This grass mixture requires only two or three mowings a season,
effectively suppresses weeds, and stabilizes the beds so they can
be used for several years without re-forming. In the future, he
may augment this combination with low-growing perennial clovers
to provide long-term habitat for beneficial insects.
No-till, no-herbicide cover crop management and vegetable planting
offer a vital soil-building weed management strategy for organic
growers and a practical solution to the kind of soil loss that prompted
the Carroll County extension agent’s original call for help.
Recent trials suggest that this approach may find broad application
in diversified vegetable production. The SST-T, manufactured by
B & B No-Till in Laurel Fork, Va., costs between $5,000 and
$10,000 for a one-row planter (depending on whether a fertilizer
hopper and/or drip tape layer are included). However, some 25 regional
Soil and Water Conservation Districts have purchased these planters
and make them available to growers on a rental basis. Morse is also
working on other ways to make this system available to small-scale
growers who cannot afford to purchase the SST-T.
Future work will reach out to more growers
Morse’s work thus far has attracted support for a new round
of soil-saving experiments over the next three years. During 2002-03,
Morse was awarded grants from the Southern Region SARE program and
the USDA Cooperative State Research, Education and Extension Service
(CSREES) to conduct further studies on no-till organic broccoli,
potato, pepper and summer squash. He hopes to extend no-till cover
crop management to a wider range of cover crops, vegetable species,
and planting seasons, and to incorporate state-of-the-art biological
pest management practices into an integrated organic production
system. (Editor’s note: The author, Mark Schonbeck was
also invited to participate in two of these projects as farm outreach
coordinator in Virginia.)
Dr. Richard McDonald, one of the region’s foremost consultants
in bio-control, will help implement 'farmscaping,' or planting strips
of flowers and herbs to provide forage and habitat for natural enemies
of key vegetable pests. The experiments will compare no-till management
of the cover crop with the traditional practice of turning the cover
crop under as a green manure several weeks before planting. They
will measure cover crop biomass, weed suppression, pest and disease
levels, marketable crop yields, and soil biological and physical
properties in the two systems.
In addition to research at Virginia Tech and University of Georgia,
the projects will include an outreach component in which organic
farmers in Virginia, North Carolina and Georgia will participate
in on-farm trials comparing no-till cover crop management with the
growers’ normal practices within a three-year vegetable rotation.
Field days will be held during the 2004 and 2005 seasons, and the
host farmers will also participate in project presentations at conferences.
Extremely wet weather during spring and summer of 2003 delayed
the establishment of many of these experiments. Morse and his colleagues
waited for weeks on end for the soil to get dry enough to plant
cover crops. We finally got a break this fall, and cover crops have
been successfully established on six acres of organic-transition
land at Kentland Farm. On-farm trials also got a late start, but
soil samples have now been taken and cover crops sown for vegetable
planting in the 2004 season.
Mark Schonbeck coordinates the outreach component of SARE-
and CSREES- funded organic no-till research projects in Virginia.
He is also editor of The Virginia Biological Farmer, the 12-page
quarterly newsletter of the Virginia Association for Biological
Farming. You can contact Mark at 540-745-4130, firstname.lastname@example.org.
For more information on VABF, write to VABF, P.O. Box 1003, Lexington,
VA 24450; visit the web site www.vabf.org, or contact our office
manager, Linda Davis at 540-463-6363.